Fuel gauging system for a motor vehicle fuel tank

ABSTRACT

A fuel gauging system for a motor vehicle fuel tank, including a housing ( 100 ) supporting a resistive element ( 200 ), an arm ( 300 ) pivotally mounted on the housing ( 100 ) and comprising at least one cursor ( 350 ) engaging the resistive element ( 200 ), and a lever ( 400 ) provided with a float connected to the arm ( 300 ) for monitoring the movements thereof. The system includes a housing ( 100 ) and an arm ( 300 ) which comprise complementary rotational guides ( 120, 310 ) and structure ( 316, 317, 318,  and  319 ) to enable translation of the arm ( 300 ) on the housing ( 100 ). The arm ( 300 ) is combined with an L-shaped lever ( 400 ) so that one of the sections ( 420 ) defines the pivot axis of the device.

The present invention relates to the field of fuel gauging devices formotor vehicle tanks.

More specifically, the present invention relates to gauging devices ofthe known type comprising a housing which bears a resistive element, anarm mounted so that it can move on the housing and comprising at leastone cursor which rests against the resistive element and a lever fittedwith a float, connected to the arm for controlling the movementsthereof.

Numerous devices of this kind have already been proposed.

Reference could, for example, be made to the documents FR-A-2661498,U.S. Pat. No. 4,870,861, DE-A-3627116, GB-A-2083628, FR-A-2533694,GB-A-1159806, GB-A-2048495, EP-A-0007072, FR-A-2364599, U.S. Pat. Nos.1,771,794, and 3,200,646.

The present invention now has the object of improving the known fuelgauging devices.

In particular, the object of the present invention is to simplify theassembly of gauging devices.

Another object of the present invention is to limit the initial size ofthe housing which houses the resistive element so as, on the one hand,to make the tests prior to installation on vehicle easier, and on theother hand, make the devices easier to store.

Another object of the present invention is to improve the reliability ofthe known gauging devices.

These objects are achieved according to the present invention by meansof a fuel gauging device, of the known type, comprising a housing whichbears a resistive element, an arm mounted so that it can pivot on thehousing and comprising at least one cursor which rests against theresistive element and a lever fitted with a float connected to the armto control the movements thereof, characterized in that the housing andthe arm comprise complementary rotational-guidance means, and means fortranslationally immobilizing the arm on the housing and that the arm isadapted to receive an L-shaped lever so that one of the branches of thelever provides the functional pivot axis of the device.

According to another advantageous feature of the invention, the meansfor translationally immobilizing the arm on the housing are formed ofsnap-fit tabs secured to the arm and adapted to interact with a bushingsecured to the housing.

Other features, objects and advantages of the present invention willbecome clear on reading the detailed description which will follow, andon studying the appended drawings which are given by way of nonlimitingexample, and in which:

FIG. 1 depicts a diagrammatic perspective view of a fuel gauging devicein accordance with the present invention,

FIG. 2 depicts a diagrammatic perspective view of a pivoting arm withwhich this device is equipped,

FIG. 3 depicts a plan view of the same arm,

FIG. 4 depicts a plan view of the gauging device of FIG. 1,

FIGS. 5 and 6 depict two sectional views of this device on sectioningplanes referenced V—V and VI—VI in FIG. 4.

FIG. 7 depicts an exploded sectional view of the fuel gauging device inFIG. 5 with a pivot arm and a level detached from a housing.

As was mentioned earlier, the gauging device in accordance with thepresent invention essentially comprises: a housing 100, a resistiveelement 200, a pivoting arm 300 and a lever 400.

The housing 100 may be produced in various alternative ways. As apreference, it is produced as a single piece by molding from plastic. Asan alternative, however, the housing 100 could be produced by assemblinga number of components.

The housing 100 essentially consists of a cage comprising a planar basewall 102 perpendicular to the axis O—O of pivoting of the arm 300 and ofa peripheral edge wall 104, which is transverse with respect to the basewall 102 and parallel to the axis of pivoting O—O.

As can be seen in particular in FIGS. 1, 4 and 5, the housing 100 ispreferably fitted, near the edge 104, and inside the latter, withseveral elastic tabs with teeth 110 designed to hold the resistiveelement 200 elastically.

According to the particular and nonlimiting embodiment illustrated inthe appended figures, four elastic tabs 110 are also provided. Theseextend from the base wall 102, appreciably parallel to the edge wall 104in the direction of the periphery of the opening of the cage 100. Eachtab 110 has a tooth 112 at its free end which is the opposite end to thebase wall 102.

The housing 100 further possesses, molded integrally with the base wall102, a cylindrical bushing 120. The latter is centered on the axis O—Oand has a central cylindrical passage 122. The bushing 120 thus extendsat right angles to the base wall 102, preferably close to the peripheralwall 104.

It will be noted that the axial end of the passage 122 pointing towardthe open periphery of the housing 100 is flared (see in particular FIGS.5 and 6) to make it easier to insert the lever 400.

The resistive element 200 is preferably formed of a planarprinted-circuit board 202 provided with a coating that defines aresistive track 204. The ends, or chosen regions of this resistive track204 are connected to pins 210-212 which pass through the edge wall 104of the housing to be accessible on the outside.

The contour of the board 202, which is preferably rectangular,complements the space defined between the tabs 110.

A person skilled in the art will understand that the printed circuitboard 200 can be fitted into the housing 100 in a position parallel tothe base wall 102, simply by translation in a direction perpendicular tothe base wall 102. The printed circuit board 200 is automatically heldin place by the tabs 110 once it has traveled past the teeth 112thereof.

The arm 300 is preferably made as one piece by molding from plastic.

According to the particular and nonlimiting embodiment illustrated inthe appended figures, the arm 300 comprises a hub 310 and a radial foot320.

The hub 310 is formed essentially of a cylindrical ring 312 equippedwith two snap-fit tabs 316-317. The ring 312 has an interior surface 313which is cylindrical of revolution, with a radius that complements theoutside radius of the bushing 120.

Thus, the hub 310 provides rotational guidance for the arm 300 on thehousing 100 when the ring 212 is engaged on the bushing 120.

The two tabs 316-317 extend parallel to the axis of the hub 310. Theyare preferably diametrically opposed with respect thereto. The tabs316-317 are each equipped, at their free end which is the opposite endto the ring 312, with a tooth 318-319 facing radially inward, that is tosay facing toward the axis of the hub 310. As can be seen in FIG. 5, theposition of the teeth 318-319 on the tabs 316-317 is such that theseteeth 318-319 rest against the rear axial end 121 of the bushing 120when the arm 300 is installed in position on the housing 100.

Thus, the tabs 316-317 equipped with teeth 318-319 have the function oftranslationally immobilizing the arm 300 on the housing 100 when the hub310 is engaged on the bushing 120.

The foot 320 is straight and planar. It extends at right angles to theaxis of the hub 310, i.e. radially with respect thereto.

As can be seen in FIGS. 2 and 5, to make it easier for the arm 300 to beengaged on the bushing 120, the radially internal surfaces of the teeth318-319 facing away from the ring 312 are bevelled toward the ring 312in the direction toward the axis thereof.

Thus, as the arm 300 is being assembled on the housing 100, the tabs316-317 are first of all deformed radially outwards, until the teeth318-319 get past the axial end 121 of the bushing 120. Once thisposition has been reached, the tabs 316-317 return to their originalposition. The ring 312 is then engaged over the outside of the bushing120 to provide rotational guidance of the arm 300, and the teeth 318-319come to rest against the axial end 121 of the bushing 120 totranslationally immobilize the arm 300.

The system in this condition is a system that can be tested. What thismeans is that the arm 300 can be pivoted about its axis of rotation O—Oon the housing 100 to check the information available between the outputpins 210-212, and if necessary adjust the resistive track 204 to obtainthe desired response as a function of the pivoting of the arm 300. Suchtesting and adjustment are possible at this stage of the assembly,according to the invention, even though the lever 400 has not yet beenplaced on the device, thanks to the fact that the arm 300 is guided inits rotation accurately about its axis and held in terms of translation.An adjustment stage of this kind, which is in itself known to thoseskilled in the art and carried out, for example, by localized attack(using a laser or the like) of the track 204 will not be describedhereafter. However, it will be noted that in this condition, the systemtakes up a small amount of space because the lever 400 has not beenfitted to the housing 100.

Of course, the arm 300 is pre-fitted with the electrically conductivecursor 350 which interacts with the resistive track 204. This cursor canbe produced in a number of ways known to those skilled in the art.

It may comprise two elastic leaves resting against a common track 204for redundancy and reliability purposes. It may alternatively comprisetwo elastic leaves resting against different resistive tracks or againstdifferent, respectively resistive and electrically conductive tracks.According to yet another alternative, as illustrated in the appendedfigures, the cursor 350 may be permanently connected to one terminal ofthe printed circuit 200 by a wire 360 which is wound in a spiral 362around the hub 310. One of the ends 364 of the wire 360 is connecteddirectly to the cursor 350 while the second end 366 of the wire 360 isconnected to a terminal of the printed circuit 200.

According to the invention, the lever 400 has an overall L shape,comprising a main leg 410 and a shorter secondary leg 420. The main leg410 is designed to take, at one of its ends, a float adapted to followthe changes in level of fuel in the tank. Such a float, which isconventional in should is not illustrated in the appended figures, inorder to simplify the illustration.

The auxiliary leg 420 is provided at the second end of the main leg 410.

The outside diameter of the auxiliary leg 420 complements the diameterof the internal passage 122 formed in the bushing 120.

Thus, via its auxiliary leg 420, the lever 400 provides the functionalpivot axis of the device, that is to say that the leg 420 provides thefunctional rotational guidance of the lever 400 and of the arm 300 onthe housing 100, more specifically with respect to the bushing 120.

To this end, receiving means 330 are provided on the arm 320 forimmobilizing the lever 400.

These immobilizing means 330 may be produced in many ways.

According to the particular embodiment illustrated in the appendedfigures, these means 330 comprise two grippers 331, 335, each formed oftwo curved jaws projecting from the exterior surface of the arm 300,more specifically from the radial foot 320 and designed in a way knownper se to trap the main leg 410 of the lever. The aforementioned jaws ofthe grippers 331, 335 are molded integrally on the arm 320. They areoriented to receive the main leg 410 of the lever 400 oriented radiallywith respect to the axis of pivoting O—O.

As a preference, the leg 320 has projecting studs 340 against which theleg 410 rests once it has been installed.

A person skilled in the art will understand that the device inaccordance with the present invention can be assembled simply bytranslating all of its components (board 200, arm 300 and lever 400 inturn) parallel to the axis O—O on the housing 100. Such assembly bytranslation along a single axis allows simple assembly by robot.

Furthermore, the possibility of testing and of adjusting the deviceprior to the fitting of the lever 400 makes it possible to limit thespace taken up by the device and makes it easier to store.

In addition, the present invention makes it possible to produce agauging device comprising a standard housing-100/board-200/arm-300assembly which can be customized by adjusting the track 204 and byfitting a lever 400 which is specifically adapted to the particularapplication envisaged, at the last moment prior to installation in agiven vehicle.

Of course, the present invention is not limited to the particularembodiment which has been described, but extends to any alternative inaccordance with its spirit.

What is claimed is:
 1. A fuel gauging device for a motor vehicle tankcomprising: a housing having a resistive element, an arm pivotallymounted to the housing and having at least one cursor which restsagainst the resistive element and a lever fitted with a float connectedto the arm to control the movements thereof, wherein the housing armcomprise complementary rotational-guidance means for translationallyimmobilizing the arm on the housing, wherein the means fortranslationally immobilizing includes two elastic snap-fit tabs, eachhaving an end and a tooth at its end, each secured to the arm andpositioned to diametrically opposed relative to the axis O—O of pivotingof the arm, said snap-fit tabs secured to the arm being adapted tointeract with a bushing secured to the housing, said lever including anL-shaped lever having two branches received on said arm so that one ofthe branches of the lever provides the functional pivot axis of thedevice, wherein said bushing includes an internal central passage thatdefines a diameter, wherein the diameter complements the branch of thelever forming the functional pivot axis of the device.
 2. The fuelgauging device of claim 1 wherein the snap-fitting tabs include rims,wherein each rim is beveled to facilitate engagement with the bushingsecured to the housing.
 3. The fuel gauging device of claim 1 whereinthe housing consists of a cage comprising a base wall perpendicularlysecured to the bushing.
 4. The fuel gauging device of claim 1 whereinthe arm carries a cylindrical hub that defines a diameter, wherein thediameter of the cylindrical hub complements that of the bushing securedto the housing.
 5. The fuel gauging device of claim 1 wherein thehousing comprises several elastic tabs adapted to hold the resistiveelement.
 6. The fuel gauging device of claim 5 wherein the elastic tabsfor holding the resistive element run perpendicular to the base wall andparallel to the axis of the bushing accommodating, with pivoting, thearm so as to allow all of the components of the device to be engaged bya translational movement parallel to the axis of pivoting of the arm. 7.The fuel gauging device of claim 1 wherein the arm comprises a hub and aradial foot provided with means for immobilizing a main leg of thelever.
 8. The fuel gauging device of claim 1 wherein the immobilizingmeans are formed of elastic grippers molded integrally on the arm.